|
by Thomas Locke, MD, MPH, Clallam County Health Officer
Smallpox is a potentially deadly infection that has plagued human civilizations for over 10,000 years. It is the first (and only) virus to be eradicated from the planet by a worldwide, multi-decade immunization campaign. By 1972, the risk of smallpox in the United States was so low that widespread vaccination was stopped. By 1980, the smallpox virus was officially declared to be eradicated and a small supply of the vaccine (containing the vaccinia virus, a close relative of cowpox) was put into deep freeze storage. Now, over twenty years later, these vaccine stockpiles are being thawed and distributed around the country for administration to military personnel and health care workers. Here are some of the questions and answers that surround the unfortunate resumption of smallpox vaccination in the United States.
Why is Smallpox Vaccination Being Resumed? Over 24 years have passed since the last human case of Smallpox. The virus still exists, officially, in laboratories in the United States and Russia. Other nations, including Iraq and North Korea, are thought to possess covert supplies of the virus. Reintroduction of smallpox into human populations is a terrifying prospect. Virtually all of the world's population is susceptible to the infection since vaccination only provides protection for about 10 years and very few people living today have had natural Smallpox infection. It is the threat of a biological terrorist attack using smallpox virus that has caused the limited resumption of smallpox vaccination.
Who will be Receiving Smallpox Vaccination? The National Smallpox Vaccination Plan, announced December 13, 2002, calls for three potential stages of vaccination. Stage 1 vaccination, to begin in early 2003, involves public health and hospital-based workers who might be called upon to respond to a smallpox outbreak in their communities. Stage 1 vaccination also involves military personnel who may be sent to combat zones where smallpox could be used as a biological weapon. All totaled, as many as 500,000 health care workers and 1 million military personnel could be vaccinated under Stage 1 guidelines.
Stage 2 vaccination would involve a much larger group of health care workers and law enforcement personnel, totaling as high as 10 million people. Stage 3 vaccination would be a nationwide campaign, only implemented in the event of a true smallpox outbreak.
Why Shouldn't Everyone be Vaccinated? Smallpox vaccine does not contain smallpox virus, but it does contain a close relative know as vaccinia virus. This virus strain was isolated in the late 19th Century and is highly effective in inducing immunity to smallpox. It can also cause serious, even life-threatening complications in a small number of people who receive the vaccine. It can be spread person to person, accidentally infecting people at high risk for complications. Smallpox vaccination is very different from the modern, highly purified, ultra-low risk vaccines of the 21st Century. It is a relatively crude, live virus vaccine that must be given by multiple punctures of the skin using a two pronged sterile needle. This method of inoculation results in a localized infection that can become very swollen and sore and shed infectious virus for up to 3 weeks. Certain health conditions dramatically increase the risk of complications from this vaccine: eczema and other chronic skin conditions, drugs or diseases that impair immune function, and pregnancy.
What are the Complications of Smallpox Vaccination? The last large scale studies of vaccine complications were done in the 1960's. At that time, about 1 in 1,000 people experienced some type of complication, usually spread of the virus beyond the initial vaccination site or to another person. Most of these complications were mild and resolved without permanent injury. As many as 1 in 20,000 people vaccinated would develop life threatening complications in which the vaccine virus overwhelmed the immune system and spread unchecked throughout the body. This complication is treated with high doses of preformed antibody to the virus. 1 to 3 out of every million people vaccinated would die as a result of the vaccine.
The risk of complications is not the same for everyone. People with eczema (or a past history of eczema) or other active skin conditions that cause breaks in the skin have an increased risk of spread of the vaccine virus over the body. People whose immune system is impaired by medications, cancer, HIV infection, or other conditions are at very high risk of life-threatening complications of the vaccine. Pregnant women and young children also have an increased risk of complications. For this reason, all people with a personal medical history of these conditions, or who live in a household where a person with one of these conditions live, will not be allowed to take the vaccine under the Stage 1 vaccination guidelines.
Do All Health Experts Agree that Smallpox Vaccination is Wise? No, there is considerable controversy about this vaccine. Usually the decision whether a vaccine is needed is based on a consideration of risks and benefits. The risks of smallpox vaccine are well known. The benefits are much more difficult to determine. If there is no exposure to smallpox, there is no benefit. No one knows what the risk of a smallpox exposure really is. Most experts believe the risk is very small. There is also controversy among respected scientists about how many people should be vaccinated. Most feel it is beneficial to have a small group of health care workers immunized in order to "jump start" a national vaccination program in the event of a bioterrorist attack with smallpox. The smallpox vaccine can be effective in preventing smallpox infection even if given up to 4 days after exposure. The United States has enough vaccine to immunize everyone in the country.
Most experts believe that some version of voluntary, Stage 1 vaccination is reasonable. Vaccination of carefully screened, fully informed health care workers who are trained in infection control techniques is likely to produce very few complications and accidental transmissions. Far fewer health experts support the notion of Stage 2 vaccination, where dozens of people are likely to die, and risks of accidental vaccine virus spread are much increased. Widespread vaccination of the U.S. population with current vaccine strains could result in hundreds to thousands of deaths and would only be justified if smallpox was once again spreading through human populations.
What Should a Person Who Wants to be Vaccinated but is not a Stage 1 Candidate Do? Health departments will not be vaccinating people who do not meet the carefully designed criteria for Stage 1 vaccination. In future years, as new supplies and types of vaccines are developed, people who wish to be vaccinated against smallpox may be able to enroll in experimental "clinical trials" of unlicensed vaccine. These trials would be offered by the vaccine manufacturers. In the event of a smallpox outbreak, all U.S. residents who are at risk of exposure will be offered smallpox vaccine free of charge.
What is the Best Protection against a Smallpox Outbreak? Smallpox is one of many naturally occurring infections that has been developed by national governments for use as a biological weapon. There are a wide range of bacteria, viruses, parasites, chemicals, and radioactive materials that could be used by terrorist governments, organizations, or individuals intent on causing widespread death and destruction. No single vaccine or medication will protect us from this disturbing array of bioterrorist agents. What will offer us the best protection is a well-developed, fully functioning emergency response system that expands our existing capacity to respond to small scale emergencies and natural disasters with new capabilities to handle biological emergencies. Public health and medical care workers will serve on the front lines of any such biological attack. Progress has been made in the last year in building up our emergency response system. We have a very long way to go before we are fully prepared. Achieving the goal of a fully prepared emergency management system will take years of hard work and billions of invested dollars. The payoff of this investment can likewise be enormous – a health care system capable of responding not only to bioterrorist threats but also the everyday infectious disease threats that kill tens of thousands of people every year.
Links:
Information about Smallpox and the Smallpox Vaccine (WA Dept. of Health)
CDC Smallpox page |
|
